Actually, the answer is both “yes” and “no”.
You see, Sundays are NEVER penitential days. Every Sunday is considered a “little Easter”. There is never a fast or an abstinence which is enacted or enforced on a Sunday. Sundays are days of celebration.
So you could indeed eat candy, if you give it up for Lent, on the Sundays of Lent. Furthermore, if you count the 40 days of Lent, if you include the Sundays of Lent you’ll find you go OVER 40 days; this is a good intimation that the Lenten season never did include “Sundays” of Lent.
HOWEVER, since the idea of penance is to give something up voluntarily, you can freely choose to continue that giving up on Sunday.
So, you CAN enjoy what you give up on a Lenten Sunday–and you CAN continue giving up what you’ve chosen to give up.
It’s your choice.